Align view to axis during modal operator?
Short answer: Nope. Sorry.

Explanation: As you correctly state, such functions are modal operators, which are a type of operator. You cannot run two operators at once. Technically, such functions as Numpad7 are operators: the operator, in this case, is bpy.ops.view3d.viewnumpad(type='TOP'). Even if you could see the View, Object, and Select menus, you wouldn't be able to do anything.

The problem's not the shortcut. It's the concept.

It would be nice for an operator to be able to be designated as AMODAL or DUAL or something like that, for an operator that does something like manipulate the view or snap the cursor to the center (another thing you can't do) so that it could be run during a modal operator's RUNNING state. Maybe one of the developers could implement this, but as of 2.68.0 r58537 it's not present.